Synthetic onion oil composition

ABSTRACT

A synthetic onion oil composition consists essentially of a blend of dialkyl disulfides and dialkyl trisulfides wherein the alkyl moiety of the di- and tri-sulfides is methyl and propyl.

United States Patent [1 1 Galetto et al.

[451 Oct. 9, 1973 SYNTHETIC ONION OIL COMPOSITION Inventors: William G.Galetto, Cockeysville; Carol A. Pace, Baltimore, both of Md.

McCormick & Company, Inc., Cockeysville, Md.

Filed: July 13, 1971 Appl. No.: 162,266

Assignee:

U.S. Cl. 426/65, 260/608 Int. Cl A231 l/26 Field of Search 99/140 R;260/608 References Cited UNITED STATES PATENTS 8/1970 Evers et a1.99/140 R 3,615,601 10/1971 Brodnitz 99/140 R OTHER PUBLICATIONS Brodnitzet a1., Gas Chromatographic Analysis Of Distilled Onion Oil, FoodTechnolog Vol. 24, (1970), PP- 78-80.

Primary Examiner-Morris O. Wolk Assistant Examiner-Sidney MarantzAttorney-Cushman, Darby & Cushman [5 7] ABSTRACT 6 Claims, No Drawings 1SYNTHETIC ONION OIL COMPOSITION This invention relates to syntheticonion oil composition and to a method 'of producing the same.

Natural onion oil is used extensively in the preparation of manyindustrially flavored food products and it is generally prepared bydistilling onions. This method of preparation, however, requiressignificant capital expenditures in terms of equipment, time and laborand thus contributes to the high cost of natural o'nion oil,

which cost, in turn, is reflected in the price of products madetherewith.

lnaccordance with the present invention, it has now been found that asynthetic onion oil composition can be prepared by a method relativelyless expensive and more simple than known methods for producing naturalonion oil. Further, the present invention advantageously provides amethod for producing a synthetic onion oil more uniform in itscomposition and flavorimparting characteristics than natural onion oil.Additionally, the method of this invention permits tailoring thecomposition and its flavor-imparting characteristics to thespecifications and desires of the user.

Thus, the present invention provides a synthetic onion oil compositioncomprising a mixture of dialkyl disulficles and dialkyl trisulfides,wherein the alkyl moiety of said disulfides and said trisulfides isselected from the group consisting of methyl and propyl. Moreparticularly, the prsent invention provides a synthetic onion oilcomposition comprising a mixture of about 30-90 weight percent of saiddialkyl disulfides and about 10-70 weight percent of said dialkyltrisulfides.

A preferred embodiment of the present invention provides a syntheticonion oil composition comprising a mixture of -10 weight percentdimethyl disulfide, -30 weight percent methyl propyl disulfide, l560weight percent dipropyl disulfide, 5-30 weight percent methyl propyltrisulfide and 5-50 weight percent dipropyl trisulfide.

The synthetic onion oil composition of this invention imparts acharacteristic onion flavor to foods and thus can effectively be usedwhenever such a flavor is desired. Generally, the amount of thecomposition employed will range from about 0.001 to 0.1 percent byweight of the food to be flavored, although it will be recognized thatthe particular amount employedcan depend on the preference of theconsumer as well as on the particular composition being utilized.

Further, the synthetic onion oil composition of this invention can beemployed in combination with edible adjuvants or carriers,conventionally employed in the flavoring or food industry such as edibleoils, sugar, salt and gums, to produce a flavoring composition.Conveniently, in such flavoring compositions, the synthetic onion oilcomposition is present in amounts ranging from about 1.0 to 30.0 weightpercent, the remainder being essentially the edible adjuvant or carrier.

The dialkyl disulfides used to prepare the synthetic onion oilcomposition of the present invention can be synthesized in accordancewith a variety of conventional procedures. Thus, unsymmetrical dialkyldisulfides can be produced by implementing conventionaldisproportionation techniques. In a typical reaction, one symmetricaldialkyl disulfide having the formula RSSR is reacted with anothersymmetrical dialkyl disulfide having the formula R'SSR' where R and Rrepresent different alkyl radicals, in the presence of an alkalinesolution in an alcohol medium. The reaction mixture is heated to refluxfor a time sufficient to attain the degree of disproportionationdesired, which can be measured or determined by monitoring the progressof the reaction using, for instance, gas-liquid chromatographictechniques. Thereafter, the product, including any unreacted alkyldisulfide, is recovered from the reaction mixture by conventionalseparating procedures. The product can then be recovered from unreactedalkyl disulfide by fractionation. Un'reacted alkyl disulfide can, ofcourse, be recycled to the disproportionation reaction zone.

Dialkyl trisulfides can be produced by reacting a dialkyl disulfide withsulfur in the presence of catalytic amounts of a basic catalyst. Thereactants can be heated to reflux for a time sufficient to produce thedesired trisulfide which can easily be recovered from the reactionmixture by distillation.

A complex mixture of symmetrical and unsymmetrical dialkyl diandtri-sulfid'es can also be produced by reacting a dialkyl disulfidehaving the formula RSSR with another dialkyl disulfide having theformula RSSR', wherein R and R are different alkyl radicals, with sulfurin the presence of a catalytic amount of a basic catalyst.

The basic catalyst used in the reactions to produce the dialkyl diandtri-sulfides can be alkali metal hydroxides, alkaline earth metalhydroxides or aliphatic amines. Preferably, an aliphatic amine such asdimethyl, dibutyl, trimethyl, triethyl, tripropyl and tributylamine, isemployed.

The invention is further illustrated by the following examples.

EXAMPLE 1 Preparation of Unsymmetrical Dialkyl Disulfide 12.8 g ofdimethyl disulfide, 15.6 g of dipropyl disulfide, 5 ml ethyl alcohol and1 g potassium hydroxide are mixed together and heated to reflux forabout 4 hours. The progress of the reaction was monitored by GLCanalysis and at the end of the 4 hour period, about 60 percent methylpropyl disulfide had been produced with about 20 percent each of thesymmetrical dialkyl disulfides remaining unreacted. The reaction mixturewas then added to 50 ml ether in a separating funnel, shaken, andallowed to separate. The upper phase containing the dialkyl disulfideswas washed twice with water, dried over MgSO and fractionally distilledto yield three fractions. The first fraction consisted essentially ofunreacted dimethyl disulfide. The second fraction consisted primarily ofmethyl propyl disulfide containing about 10-15 percent dipropyldisulfide, while the third fraction consisted essentially of dipropyldisulfide.

EXAMPLE 2 Preparation of Symmetrical Trisulfides g of dipropyldisulfide, 39 g of sulfur'and 7.5 g of dibutyl amine are heated in anoil bath at C for 5 hours. The resulting reaction product is cooled,ether extracted, washed twice with dilute l-lCl, washed twice with waterand then dried over CaCl The product is then vacuum distilled to yield73.3 g of a fraction having a B.P. of 94-l00C at 3-4 mini-lg, which is amixture of 80-90 percent dipropyl trisulfide and 10-20 percent dipropyldisulfide.

EXAMPLE 3 Preparation of Complex Mixture of Diand Tri- Sulfides 128.0 gof dimethyl disulfide, 312.0 g of dipropyl disulfide, 70 g of sulfur and5.0 ml of dibutyl amine were mixed together and heated to reflux for 10hours in a 130C oil bath and 8 hours in a 150C oil bath. The resultingreaction product was vacuum distilled at 3-4 mml-lg, 409.7 g ofdistillate being recovered. The distillate consisted essentially ofabout 7 percent dimethyl disulfide, about 24 percent methyl propyldisulfide, about 51 percent dipropyl disulfide, about 12 percent methylpropyl trisulfide and about 6 percent dipropyl trisulfide. Thisdistillate provides an acceptable synthetic onion oil composition.

EXAMPLE 4 A synthetic onion oil composition was prepared by mixingtogether:

The complex dialkyl diand tri-sulfide mixture of Example 3 269.6 g Thedipropyl diand tri-sulfide mixture of Example 2 35 g The resultingmixture was spray dried at an outlet temperature of 115C and provided asynthetic onion oil composition similar in flavor and strength tonatural spray dried onion oil.

EXAMPLE The procdure outlined in Example 3 was repeated to produceessentially the distillate. as defined therein which was then vacuumdistilled to yield the following four fractions:

Fraction 1 B.P. 36-42C, 0.5 mm Hg about 40 percent methyl propyldisulfide, about 50% dipropyl disulfide and about methyl propyltrisulfide-5.65 g.

Fraction 2 B.P. 42-60C, -.5 mm Hg about 60 percent dipropyl disulfide,about 35 percent methyl propyl trisulfide, and about 5 percent dipropyltrisulfide 6.66 g.

Fraction 3 B.P. 60-67C 0.5 mm Hg about 65 percent dipropyl trisulfide,about 30 percent methyl propyl trisulfide, and about 5 percent methylpropyldisulfide and dipropyl disulfide.

Fraction 4 B.P. 67-7 0C. Very similar to Fraction 3. Fractions 3 and 4,7.49 g

A synthetic onion oil composition was prepared by admixing 5.65 gFraction 1, 7.49 g Fractions 3 and 4 and 0.03 g dipropyl disulfide.

As can be seen from the above a variety of procedures can be employed toproduce the component dialkyl diand tri-sulfides of the synthetic onionoil composition of this invention. Methods other than those specificallyexemplified above include the Bunte salt method, potassium ferricyanideoxidation of mercaptans as well as iodine oxidation of mercaptans.

Other synthetic onion oil compositions can also be produced byproviding, for instance, a different combination of fractions producedin Example 5. Still another synthetic onion oil compositions areprepared by admixing with the second fraction produced in Example l, thethird and fourth fractions obtained in Example 5.

We claim:

1. A synthetic onion oil composition consisting essentially of a blendof dialkyl disulfides and dialkyl trisultides, wherein the alkyl moietyof said diand trisulfides is selected from the group consisting ofmethyl and propyl, said dialkyl disulfides being present in amounts ofabout 30-90 percent by weight of said composition and said dialkyltrisulfides being present in amounts of about l0-70 percent by weight ofsaid composition.

2. The synthetic onion oil composition of claim 1 consisting essentiallyof 0-10 weight percent dimethyl disulfide, 10-30 weight percent methylpropyl disulfide, 15-60 weight percent dipropyl disulfide, 5-30 weightpercent methyl propyl trisulfide and 5-50 weight percent dipropyltrisulfide.

3. A food flavored with a synthetic onion oil composition present inamounts of about 0.001 to 0.1 percent by weight of said food, saidsynthetic onion oil composition consisting essentially of a blend ofdialkyl disulfides and dialkyl trisulfides, wherein the alkyl moiety ofsaid diand tri-sulfides is selected from the group consisting of methyland propyl, said dialkyl disulfides being present in amounts of about30-90 percent by weight of said composition and said dialkyl trisulfidesbeing present in amounts of about 10-70 percent by weight of saidcomposition.

4. The food of claim 3 wherein said synthetic onion oil compositionconsists essentially of 0-10 weight percent dimethyl disulfide, 10-30weight percent methyl propyl disulfide, 15-60 weight percent dipropyldisulfide, 5-30 weight percent methyl propyl trisulfide and 5-50 weightpercent dipropyl trisulfide.

5. A flavoring composition comprising an edible carrier and a syntheticonion oil composition present in amounts of about 1.0 to 30.0 weightpercent of said flavoring composition, said synthetic onion oilcomposition consisting essentially of a blend of dialkyl disulfides anddialkyl trisulfides, wherein the alkyl moiety of said diand tri-sulfidesis selected from the group consisting of methyl and propyl, said dialkyldisulfides being present in amounts of about 30-90 percent by weight ofsaid synthetic onion oil composition and said dialkyl trisulfides beingpresent in amounts of about 10-70 percent by weight of said syntheticonion oil composition.

6. The flavoring composition of claim 5 wherein said synthetic onion oilcomposition consists essentially of 0-10 weight percent dimethyldisulfide, 10-30 weight percent methyl propyl disulfide, 15-60 weightpercent dipropyl disulfide, 5-30 weight percent methyl propyl trisulfideand 5-50 weight percent dipropyl trisulfide. =l=

2. The synthetic onion oil composition of claim 1 consisting essentiallyof 0-10 weight percent dimethyl disulfide, 10-30 weight percent methylpropyl disulfide, 15-60 weight percent dipropyl disulfide, 5-30 weightpercent methyl propyl trisulfide and 5-50 weight percent dipropyltrisulfide.
 3. A food flavored with a synthetic onion oil compositionpresent in amounts of about 0.001 to 0.1 percent by weight of said food,said synthetic onion oil composition consisting essentially of a blendof dialkyl disulfides and dialkyl trisulfides, wherein The alkyl moietyof said di- and tri-sulfides is selected from the group consisting ofmethyl and propyl, said dialkyl disulfides being present in amounts ofabout 30-90 percent by weight of said composition and said dialkyltrisulfides being present in amounts of about 10-70 percent by weight ofsaid composition.
 4. The food of claim 3 wherein said synthetic onionoil composition consists essentially of 0-10 weight percent dimethyldisulfide, 10-30 weight percent methyl propyl disulfide, 15-60 weightpercent dipropyl disulfide, 5-30 weight percent methyl propyl trisulfideand 5-50 weight percent dipropyl trisulfide.
 5. A flavoring compositioncomprising an edible carrier and a synthetic onion oil compositionpresent in amounts of about 1.0 to 30.0 weight percent of said flavoringcomposition, said synthetic onion oil composition consisting essentiallyof a blend of dialkyl disulfides and dialkyl trisulfides, wherein thealkyl moiety of said di- and tri-sulfides is selected from the groupconsisting of methyl and propyl, said dialkyl disulfides being presentin amounts of about 30-90 percent by weight of said synthetic onion oilcomposition and said dialkyl trisulfides being present in amounts ofabout 10-70 percent by weight of said synthetic onion oil composition.6. The flavoring composition of claim 5 wherein said synthetic onion oilcomposition consists essentially of 0-10 weight percent dimethyldisulfide, 10-30 weight percent methyl propyl disulfide, 15-60 weightpercent dipropyl disulfide, 5-30 weight percent methyl propyl trisulfideand 5-50 weight percent dipropyl trisulfide.